To prevent leakage of body exudates from absorbent articles such as feminine care pads or napkins and disposable diapers, it is desirable that the exudates not reach the edges of the absorbent material in the article. A xe2x80x9ccenter fillxe2x80x9d strategy is desirable for leakage control, wherein fluids are preferentially held in a central region of the article. Unfortunately, in traditional absorbent articles, there is generally no barrier to bulk flow or capillary wicking from the target region to the edges of the article, so leaking from the edges of the article is a persistent problem. Thus, in traditional articles, fluid entering the center of the article still has the potential to travel to the sides and leak. Flow from the center to the sides can be especially rapid when the article is compressed, bringing the wet central portion of the article in contact with absorbent material at the sides of the article.
The ability of an absorbent article to promote center fill and reduce leakage depends on the goodness of body fit achieved by the article in use. In sanitary napkins and other absorbent articles, the article as worn is often compressed laterally by the legs of the wearer, causing significant deformation of the article. In many conventional articles, the deformation is random or uncontrolled, resulting in a variety of product configurations that often may be inadequate for good uptake and fluid distribution in the article.
Past efforts to improve body fit and promote liquid uptake in the center of the article have included three-dimensional structures with elevated central members resting above the plane of a flat absorbent core. The elevated member can be a cylinder or an inverted U-shaped tube, for example. However, the elevated member adds substantially to the bulk of the article, potentially reducing comfort when worn and certainly decreasing packaging efficiency since fewer articles can fit into a package when the articles are no longer flat. Further, the article with an elevated central member can still suffer from leakage and smearing from fluid leaving the sides of the member.
Many other articles have been proposed for either improved body for or leakage protection which suffer from complexity of design and high cost, with multiple components comprising a variety of absorbent materials in the absorbent core.
What is needed is an article with good center fill performance that can reduce leakage to the sides of the article and provide good body fit with a simplified, low-cost absorbent core.
It has been discovered that a useful absorbent article with good leakage control can be produced with an absorbent core comprising a unitary absorbent layer and a thin, flexible wicking barrier, such as a polymeric film, which passes through the unitary absorbent layer along a portion of a boundary dividing the unitary absorbent layer into a central portion and an outer portion, wherein the two portions are nevertheless contiguous. The boundary comprises at least one slit and desirably two spaced apart slits through which the wicking barrier passes and further comprises a joining zone contiguously connecting the central portion with the outer portion. The interaction of the wicking barrier with the central and outer portions of the unitary absorbent layer results in an absorbent article having excellent leakage control and body fit. Further, the article offers a simple design in which a single piece of absorbent material forms the primary absorbent layer yet has multiple portions with fluid isolation therebetween provided by a wicking barrier. In a preferred embodiment, body fit is further enhanced by a deflection control element cooperatively associated with the central portion of the unitary absorbent layer.
As used herein, the term xe2x80x9cunitaryxe2x80x9d means that all portions of a component are joined together without a physical discontinuity such as a gap or cut completely separating or severing one portion from another. Thus, a unitary object could be a single piece of a web provided with slits that do not completely sever the web into two or more pieces, or a single section of a laminated absorbent material with each ply bonded to adjacent plies. A section of web with a central cutout region that can be completely removed from the web without any need for tearing or cutting or disengaging entangled fibers is not unitary, even if the cutout section is placed back onto the web, for a physical discontinuity clearly has been created by the process of removing or cutting out one section.
Hence, in one aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having two longitudinal sides, a target zone and a body side, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) an absorbent core disposed between the topsheet and the backsheet comprising a unitary absorbent layer having a thickness, the unitary absorbent layer comprising a central portion and an outer portion separated in part by one or more slits passing through the thickness of the unitary absorbent layer and further comprising a boundary between the outer portion and the central portion; and
d) a wicking barrier spanning a horizontal distance above the body-side surface of the outer portion of the unitary absorbent layer and spanning a vertical distance in the one or more slits of the unitary absorbent layer.
In another aspect, the invention resides in an absorbent article for use on the body of a wearer, the absorbent article having two longitudinal sides, a target zone and a body side, the absorbent article comprising:
a) a liquid impervious backsheet;
b) a liquid pervious topsheet attached to the backsheet;
c) a unitary absorbent layer disposed between the topsheet and the backsheet, the unitary absorbent layer having a thickness, and comprising a central portion and an outer portion separated by a boundary comprising a slit; and
d) a wicking barrier spanning a horizontal distance on the surface of the outer portion of the unitary absorbent layer and spanning the thickness of the unitary absorbent layer in a portion of the slit.
In another aspect, the invention resides in a method of making an absorbent article having a body-side comprising:
a) providing a layer of absorbent material;
b) slitting a portion of the layer of absorbent member to define a central portion and an outer portion of the absorbent layer with a boundary separating the central portion from the outer portion, wherein the boundary comprises at least one slit and a joining zone between ends of the at least one slit, the joining zone connecting the outer portion to the central portion;
c) providing a first section of wicking barrier material along a portion of the boundary between the central portion and the outer portion of the layer of absorbent material, wherein the wicking barrier material spans a vertical distance in the layer of absorbent material;
d) providing a second section of wicking barrier material on or above the body-side surface of the outer portion of the layer of absorbent material;
e) sandwiching the layer of absorbent material a topsheet and a backsheet to form an absorbent article.
In still another aspect, the invention resides in a method of making an absorbent article having a body-side comprising:
a) providing a unitary layer of absorbent material;
b) providing the unitary layer of absorbent member with at least one slit that forms a longitudinal boundary dividing the longitudinal sides of a central portion of the unitary layer from an outer portion of the unitary layer;
c) inserting a segment of wicking barrier material through a portion of the slit to form a vertical wicking barrier between part of the central portion of the unitary layer and the outer portion of the unitary layer;
d) further providing a horizontal component of a wicking barrier above the body-side surface of the unitary layer to form a composite of a unitary layer and one or more wicking barrier materials;
e) disposing the composite above a backsheet;
f) disposing a topsheet above the composite;
g) attaching the topsheet to the backsheet.
The central portion of the unitary absorbent layer is adapted to receive fluid flow from the body of the wearer or from other fluid sources. Leakage from the longitudinal sides of the article is reduced or prevented by the wicking barrier between the central portion and the outer portion of the article in the target zone (e.g., the crotch region).
The wicking barrier spans a vertical distance in the absorbent core to effectively impede laterally outward flow from the central portion to the outer portion in the target zone. For best results, the wicking barrier extends vertically at least the thickness of the absorbent core, though it can also extend vertically a fraction of the thickness of the core (e.g., 50% or greater). The wicking barrier can be a film or strip of barrier material that has been inserted into one or more slits to span a vertical distance in the absorbent core and desirably to also span a horizontal distance on the body-side surface of the absorbent core, and preferably on the body-side surface of the outer portion thereof. In one preferred embodiment, the barrier material covers a substantial portion of the body-side surface of the outer portion of the absorbent core in the target zone and between the longitudinal sides of the absorbent article and the central portion of the unitary absorbent layer, then descends into spaced apart slits on the boundary around the central portion, and passes beneath at least a portion of the central portion along the garment-side surface of the unitary absorbent layer. The wicking barrier can be provided with apertures in the region beneath the central portion of the unitary absorbent layer to permit some degree of fluid flow therethrough, particularly to permit fluid flow to an absorbent layer residing below the central portion of the unitary absorbent layer.
The wicking barrier is typically a separate component that is not integral with other components of the article. However, it can also comprise material from the backsheet or topsheet. Thus, in one embodiment, the wicking barrier is integral or unitary with the backsheet, and comprises an extended portion of the backsheet which wraps part of the outer portion of the unitary absorbent layer and penetrates through opposing slits in the unitary absorbent layer, separating the outer portion from the central portion of the unitary absorbent layer. Less desirably, the wicking barrier can comprise material from the topsheet that penetrates into the absorbent core to separate the central portion from the outer portion of the unitary absorbent layer, wherein when the topsheet material that penetrates into the core is rendered substantially liquid impervious by chemical treatment, impregnation of adhesive or thermoplastic material, heat sealing, or the like.
The central portion, being partially separated from the outer portion by the presence of slits and a wicking barrier, can also be adapted to deflect upward toward the body of the wearer during inwardly lateral compression of the absorbent article in the target zone. In several embodiments, the central portion is relatively free to deflect upward substantially independently of the deflection of the surrounding outer portion of the absorbent core. Desirably, the combinations of slits and a wicking barrier permit the central portion to conform to the body during use by virtue of upward deflection.
A single slit along the boundary may curve to circumscribe a portion of the central portion of the unitary absorbent layer. The boundary can also include two or more spaced apart slits. Generally, the boundary further comprises a linear region (e.g., an imaginary line or elongated zone) herein defined as the xe2x80x9cjoining zonexe2x80x9d which joins the ends of the slit or slits and provides a continuous span of absorbent material from the central portion to the outer portion of the unitary absorbent layer. In an article with a front end and a back end and having longitudinal slits, the boundary includes the slits and a line joining the front ends of the slits and a line joining the back ends of the slits. In an article with a right side and a left side and having a pair of spaced apart, substantially transverse slits, the boundary includes the slits and the line joining the right ends of the slits and the line joining the left end of the slits. In other words, the boundary comprises one or more slits and one or more joining zones between the ends of the one or more slits, wherein the one or more joining zones contiguously join the central portion to the outer portion.
In one embodiment, two or more sides of a central portion of the unitary absorbent layer are circumscribed by one or more slits such that only a single substantially linear region (a single linear joining zone) joins the central portion to the outer portion of the unitary absorbent layer, wherein the linear region joining the two portions serves as a hinge zone that permits the central portion to be lifted away from the plane of the unitary absorbent layer except for the material in the hinge zone, such that a wicking barrier or other object can be readily placed underneath the central portion, and such that portions of the wicking barrier can extend across the body-side surface of the outer portion of the unitary absorbent layer in the target zone. The hinge zone can be impregnated with hydrophobic material to prevent wicking therethrough.
Many articles of the present invention are intended to be worn in the crotch of a wearer, and thus have crotch regions. However, the present invention can also be applied to other articles such as underarm pads or wound dressings where a crotch region may not exist. In such cases, the article will have a region where fluid intake is intended to occur, termed the xe2x80x9ctarget region.xe2x80x9d The portion of the article including the longitudinal length of the target region and the full transverse width of the article normal to length of the target region is defined herein as the xe2x80x9ctarget zone.xe2x80x9d For articles intended to be worn in the crotch, the terms xe2x80x9ctarget zonexe2x80x9d and xe2x80x9ccrotch regionxe2x80x9d are generally synonymous, whereas xe2x80x9ctarget regionxe2x80x9d generally excludes the portions of the absorbent core near the longitudinal sides since the intended area for fluid intake is generally substantially central in the absorbent article.
Opportunities for improved body fit are especially great if a deflection control element is disposed beneath or within the absorbent core, and particularly beneath or within the central portion of the absorbent core, whereby the central portion is urged toward the body of the wearer during use of the article. The deflection control element can be selected from a variety of elements or structures designed to influence the compressed shape of the article when worn and to urge the central portion of the absorbent core toward the body of the wearer or, more generally, toward a source of liquid exudates.
The deflection control element may be any of the following or a combination thereof:
1. a central rising member which deflects upward when compressed from the sides;
2. a central inflatable member or other inflatable member;
3. a relatively narrow pledget of absorbent material which forces the overlying unitary absorbent layer to assume a convex upward shape predisposing the unitary absorbent layer to deflect upward during laterally inward compression in the target zone or crotch region; and
4. bending lines and specifically shaping lines which influence bending of the central portion of the unitary absorbent layer.
The absorbent article in general can comprise a central rising member or central inflatable member in or beneath the unitary absorbent layer and preferably beneath the central portion of the unitary absorbent layer. Central rising members, central inflatable members, and related structures are described more fully in commonly owned, copending application U.S. Ser. No. unknown, xe2x80x9cCenter Fill Absorbent Article with Central Rising Memberxe2x80x9d, by Chen et al. and U.S. Ser. No. unknown, xe2x80x9cAbsorbent Article with Central Pledget and Deformation Controlxe2x80x9d, by Chen et al., both filed on the same day as the present application.
The use of a central rising member or central inflatable member under a central portion of the unitary absorbent layer is particularly effective in combination with a wicking barrier. Desirably, a portion of the wicking barrier also resides on the body-side surface of the absorbent core, particularly on the body-side surface of the outer portion of the unitary absorbent layer in the target zone. The wicking barrier serves to prevent lateral wicking of fluid to the longitudinal sides of the article and, when provided with a horizontal component on the surface of the absorbent core, serves to prevent fluid communication between the central portion of the unitary absorbent layer and the outer portion thereof when the article is bunched together in use. The wicking barrier can also help control the geometry of the absorbent article when in use under dynamic conditions, permitting flexure or folding such that the central portion of the unitary absorbent layer is urged toward the body or such that the topsheet of the article effectively contacts the body.
Good body fit can be promoted by the central rising member disposed in or beneath the absorbent core, preferably beneath the central portion of the unitary absorbent layer, wherein the central rising member deflects upward upon lateral compression from the longitudinal sides of the article. The deflection of the central rising member in turn deflects the central portion of the unitary absorbent layer upward toward the body of the wearer for good body fit. In conjunction with a central rising member, a wicking barrier separating the central portion from the outer portion can also permit or promote a degree of independent motion or deflection of the central portion toward the body. Similar effects can be achieved with a central inflatable member which deflects the central portion of the unitary absorbent layer toward the body and increases the three-dimensional nature of the absorbent article in use for improved leakage control.
Proper deformation of the absorbent core during use can also be promoted by one or more shaping lines and/or one or more crease lines in the absorbent core. A crease line, when used, generally lies along the boundary of the outer portion of the unitary absorbent layer or away from the central portion and promotes downward folding or bending of the article along the crease line (e.g., a valley fold) during lateral compression from the longitudinal sides of the article. A shaping line promotes upward folding or bending (e.g., a mountain fold) during lateral compression from the longitudinal sides of the article. A shaping line, if present, generally resides along or near the longitudinal centerline and typically will be primarily contained in the central portion of the unitary absorbent layer. A shaping line desirably coupled with at least two crease lines works to establish a W-fold geometry in the article when laterally compressed, offering good control over the upward deflection of the central portion in the absorbent core. Crease lines and shaping lines, as defined therein, will be generally referred to hereafter as xe2x80x9cbending lines.xe2x80x9d Bending lines can be formed by one of more treatment methods such as embossing, stamping, or other known methods for creating densified regions, as described in U.S. Pat. No. 4,655,759, issued Apr. 7, 1987 to A. Y. Romans-Hess et al. Other methods for line formation include slitting; cutting; notching; tearing; thermobonding (application of heat to create bonding, particularly with thermoplastic materials or heat-setting resins); hot pressing (simultaneous application of heat and pressure, especially in conjunction with thermoplastic binder materials, thermosetting plastics, or heat setting resins); ultrasonic bonding; perforating; perf-embossing; needling; impregnation by resins, waxes, or thermoplastics; hydraulic cutting by water jets or other fluid jets; pre-folding; creasing; scoring; or removing material by abrasion, ablation, picking, scraping, or suction.
In certain embodiments, then, the crease lines and shaping lines may be a series of perforations, notches, cuts, tears, or slits optionally having portions not fully perforated, notched, cut, torn, or slit along a line""s length for increased integrity. Crease lines and shaping lines formed by slitting or creation of densified areas are believed to be especially useful due to their ease of application and general effectiveness.
The length spanned by the shaping line or lines in the longitudinal direction can be at least about 1 cm, specifically at least about 2 cm, more specifically from about 3 cm to about 10 cm, more specifically still from about 4 cm to about 8 cm, and most specifically from about 4 cm to about 6 cm. In sanitary napkins and other absorbent articles, a longitudinal slit or notch, if present, desirably can be from about 4 cm to about 6 cm long. The longitudinal length of the crease lines can be smaller than that of the shaping lines, but in most embodiments desirably is about the same as or longer than that of the shaping line. For example, the crease lines can be longer than the shaping lines in the longitudinal direction by at least about 1 cm, more specifically at least about 2 cm, more specifically at least about 3 cm, and most specifically from about 2.5 cm to 5 cm.
In one embodiment, the central rising member can be a resilient material folded or rolled into the shape of the letter xe2x80x9cexe2x80x9d such that lateral compression from the sides causes the upper section of the folded shape to deflect upwards. Other configurations can achieve the same purpose. The central rising member generally has flexure points or folded sections, such as is found in an xe2x80x9cexe2x80x9d-folded web, such that lateral compression from the longitudinal sides of the central rising member causes at least a portion of the central rising member to deflect upwards with sufficient force that an overlying central absorbent member can be deflected toward the body (or that the central rising member itself can rise toward the body when it serves as the central absorbent member). An absorbent central rising member can also be configured as a flattened tube or an equivalent. Other shapes can also be effective, such as a layer of absorbent material folded or held in the shape of the letter xe2x80x9cCxe2x80x9d rotated 90 degrees to the right, similar to an inverted xe2x80x9cUxe2x80x9d with the ends brought together. The rotated xe2x80x9cCxe2x80x9d shape is especially useful when the internal void space therein is partially filled with another section of absorbent material to prevent collapse and to help predispose the shape to flex upward during lateral compression.
Possible uses of the present invention include absorbent articles for intake, distribution, and retention of human body fluids. Examples include feminine care pads and related catamenial devices or sanitary napkins, including xe2x80x9cultra-thinxe2x80x9d pads and pantiliners and maxipads. Likewise, the present invention can be applied to diapers, disposable training pants, other disposable garments such as swimming garments, incontinence articles, bed pads, bandages, wound dressings, and other absorbent articles.
For feminine care pads in particular, the present invention offers surprising advantages. The presence of one or more slits in the boundary between the central portion and the outer portion of the unitary absorbent layer, coupled with the presence of a wicking barrier, can reduce stiffness of the article, reduce leakage of fluid toward the sides of the article, improve the ability of the central portion to conform to the body, reduce fluid flow on the surface of the article, and improve opportunities for controlled deformation of the article when worn. The presence of a wicking barrier with a vertical component in the target zone frequently appears useful in promoting a W-shape geometry of sanitary napkins when compressed in use which can rise toward the body for better intake of fluid and better fit in general. Further still, the center-fill strategy made possible by the present invention can be used to generally ensure that the outer portion remains relatively dry under typical usage conditions, which in turn allows the outer portion of the unitary absorbent layer to better maintain its shape and to help hold the pad in a comfortable and effective position, even as the central portion of the unitary absorbent layer receives a substantial quantity of fluid to absorb.
As used herein, a material is said to be xe2x80x9cabsorbentxe2x80x9d if it can retain an amount of water equal to at least 100% of its dry weight as measured by the test for Intrinsic Absorbent Capacity given below (i.e., the material has an Intrinsic Absorbent Capacity of at about 1 or greater). Desirably, the absorbent materials used in the absorbent members of the present invention have an Intrinsic Absorbent Capacity of about 2 or greater, more specifically about 4 or greater, more specifically still about 7 or greater, and more specifically still about 10 or greater, with exemplary ranges of from about 3 to about 30 or from about 4 to about 25 or from about 12 to about 40.
As used herein, xe2x80x9cbulkxe2x80x9d and xe2x80x9cdensity,xe2x80x9d unless otherwise specified, are based on an oven-dry mass of a sample and a thickness measurement made at a load of 0.34 kPa (0.05 psi) with a 7.62-cm (three-inch) diameter circular platen. Thickness measurements of samples are made in a TAPPI-conditioned room (50% relative humidity and 23xc2x0 C.) after conditioning for at least four hours. Samples should be essentially flat and uniform under the area of the contacting platen. Bulk is expressed as volume per mass of fiber in cc/g and density is the inverse, g/cc.
As used herein, the term xe2x80x9ccellulosicxe2x80x9d is meant to include any material having cellulose as a major constituent, and specifically comprising at least 50 percent by weight cellulose or a cellulose derivative. Thus, the term includes cotton, typical wood pulps, nonwoody cellulosic fibers, cellulose acetate, cellulose triacetate, rayon, thermomechanical wood pulp, chemical wood pulp, debonded chemical wood pulp, milkweed, or bacterial cellulose.
As used herein, the xe2x80x9ccrotch regionxe2x80x9d of an absorbent article refers to the generally central region that will be in contact with the crotch of the user, near the lowermost part of the torso, and resides between the front and rear portions of the article. Typically the crotch region contains the transverse centerline of the article and generally spans approximately 7 to 10 cm in the longitudinal direction.
As used herein, the term xe2x80x9cextensiblexe2x80x9d refers to articles that can increase in at least one of their dimensions in the x-y plane by at least 10% and desirably at least 20%. The x-y plane is a plane generally parallel to the faces of the article. The term extensible includes articles that are stretchable and elastically stretchable (defined below). In the case of a sanitary napkin comprising an absorbent core, for example, the article and the absorbent core are desirably extensible both in length and width. The absorbent article, however, may only be extensible in one of these directions. Preferably, the article is extensible at least in the longitudinal direction. Examples of extensible materials and articles, and their methods of preparation, are disclosed in U.S. Pat. No. 5,611,790, issued Mar. 18, 1997 to Osborn III, herein incorporated by reference in its entirety.
As used herein, the term xe2x80x9cflexure-resistantxe2x80x9d refers to an element which will support a bending moment, in contrast to an element which will support only axial forces. Likewise, as used herein, xe2x80x9cflexure resistancexe2x80x9d is a means of expressing the flexibility of a material or article and is measured according to the Circular Bend Procedure described in detail in U.S. Pat. No. 5,624,423, issued Apr. 29, 1997 to Anjur et al., herein incorporated by reference in its entirety. Flexure resistance is actually a measurement of peak bending stiffness modeled after the ASTM D4032-82 Circular Bend Procedure. The Circular Bend Procedure of Anjur et al. is a simultaneous multidirectional deformation of a material in which one face of a specimen becomes concave and the other face becomes convex. The Circular Bend Procedure gives a force value related to flexure-resistance, simultaneously averaging stiffness in all directions. For comfort, the absorbent article desirably has a flexure-resistance of less than or equal to about 1,500 grams, more specifically about 1000 grams or less, more specifically still about 700 grams or less and most specifically about 600 grams or less. For shaping performance, the unitary absorbent layer can have a flexure resistance of at least about 30 grams, more specifically at least about 50 grams, and most specifically at least about 150 grams.
As used herein, the term xe2x80x9chorizontal,xe2x80x9d refers to directions in the plane of the article that are substantially parallel to the body-side surface of the article, or, equivalently, substantially normal to the vertical direction of the article, and comprises the transverse direction and the longitudinal direction of the article, as well as intermediate directions.
As used herein, the term xe2x80x9chydrophobicxe2x80x9d refers to a material having a contact angle of water in air of at least 90 degrees. In contrast, as used herein, the term xe2x80x9chydrophilicxe2x80x9d refers to a material having a contact angle of water in air of less than 90 degrees.
As used herein, xe2x80x9chydrostatically liquid resistantxe2x80x9d refers to material having a hydrostatic head of at least about 25 centimeters as determined in accordance with the standard hydrostatic pressure test AATCCTM No.127-1977 with the following exceptions: (1) The samples are larger than usual and are mounted in a stretching frame that clamps onto the cross-machine direction ends of the sample, such that the samples may be tested under a variety of stretch conditions (e.g., 10%, 20%, 30%, 40% stretch); and (2) The samples are supported underneath by a wire mesh to prevent the sample from sagging under the weight of the column of water.
As used herein xe2x80x9cliquid resistantxe2x80x9d refers to the property of a material which impedes the transport of liquids through and past such material and is inclusive of liquid impervious materials.
As used herein, the term xe2x80x9cpolymeric webxe2x80x9d refers to a porous or nonporous layer primarily composed of polymeric material, and can be a nonwoven web, a plastic film, a polymeric film, an apertured film, or a layer of foam. Polymeric webs can be used as wicking barriers, baffle layers, backsheets, and, if sufficiently liquid pervious, as topsheets of absorbent articles. A polymeric web can consist of about 50 weight percent or more polymeric material, more specifically about 80 weight percent or more polymeric material, and most specifically about 90 weight percent or more polymeric material. Exemplary materials include polyolefins, polyesters, polyvinyl compounds, and polyamides.
As used herein, the term xe2x80x9ctransversexe2x80x9d refers to a line, axis, or direction which lies within the plane of the absorbent article and is generally perpendicular to the longitudinal direction. The z-direction is generally orthogonal to both the longitudinal and transverse centerlines. The term xe2x80x9clateralxe2x80x9d refers to substantially in-plane directions having a predominately transverse component. Likewise, xe2x80x9cinwardly lateral compressionxe2x80x9d refers to compression directed from the longitudinal sides of an article toward the longitudinal centerline thereof, applied substantially in the transverse direction.
The absorbent article comprising an absorbent core can, in addition to being extensible, also be stretchable. The term xe2x80x9cstretchablexe2x80x9d, as used herein, refers to articles that are extensible when stretching forces are applied to the article and offer some resistance to stretching. The terms xe2x80x9celastically stretchablexe2x80x9d or xe2x80x9celastically extensiblexe2x80x9d are intended to be synonymous. These terms, as used herein, mean that when in-plane stretching forces are removed, the article or absorbent fibrous structure will tend to return toward its unextended or unstretched dimensions (or original dimensions). It need not return all the way to its unstretched dimensions, however. It may return to relaxed dimensions between its unstretched dimensions and extended (or stretched dimensions).
In preferred embodiments wherein the central portion of the unitary absorbent layer is deflected upward toward the body during lateral compression, the degree of elevation of the central portion of the unitary absorbent layer can be quantified in terms of a Vertical Deformation test. As used herein, xe2x80x9cVertical Deformationxe2x80x9d refers to the height increase experienced by the body-side surface of an absorbent article when the longitudinal sides in the crotch reason are gripped and steadily moved inward toward the longitudinal axis of the article, decreasing the span between the longitudinal sides by 1.5 cm. The Vertical Deformation test apparatus comprises two clamps having a clamp width (longitudinal length of the clamped portion of the edge of the article) of 5 cm. One clamp is stationary and the other is on a track that permits the clamp to slide to increase or decrease the distance between the clamps while keeping the clamp aligned and parallel to the other clamp. The clamps should be tilted downward at an angle of 20 degrees relative to horizontal, such that both outer edges of the absorbent article are slightly elevated relative to the nearest crease line, thus somewhat simulating the positioning of the outward edges of the absorbent article that may be induced by panties with elevated elastic edges in the target zone. The clamps are 5 cm above the surface of the track, permitting a pad to be suspended in air between the clamps, gripped in the crotch area such that a portion of the longitudinal sides of the absorbent core are held, with the clamps extending inward no more than about 3 mm from the outer edge of the absorbent core. The article should be held substantially taut in the region between the clamps without damaging the article, such that the target zone is substantially horizontal before lateral compression begins. At a rate of about 0.5 centimeters per second (cm/s), the slidable clamp is moved smoothly toward the fixed clamp by a distance of 50% of the initial width of the article in the target zone (or less if the article become incompressible such that more than about 5 kg of force is required to further compress the article). The height of the center of the pad or absorbent article is recorded before the clamp is moved and after the clamp is moved, yielding a difference that is reported as the Vertical Deformation. An increase in height is reported as a positive number, while a decrease is reported as a negative number. Desirably, the Vertical Deformation of the absorbent article is at least about 0.5 cm. Specifically, the Vertical Deformation is at least about 1 cm, and more specifically is at least about 1.5 cm and up to about 10 cm. Desirably, an absorbent article of the present invention exhibits an increase in Vertical Deformation in the target zone (specifically, the crotch region) of at least about 20%, and more specifically at least about 50%, relative to the Vertical Deformation in the target zone exhibited by an essentially identical absorbent article without a shaping line.
As used herein, xe2x80x9cCentral Elevationxe2x80x9d is defined as the height difference between the center of the central portion of the unitary absorbent layer along the transverse centerline of the article and the average height of the longitudinal sides of the outer portion of the unitary absorbent layer along the transverse centerline of the article at the end of the Vertical Deformation Test as described above. The Central Elevation for absorbent articles of the present invention can be at least about 0.5 cm, specifically at least about 1 cm, and more specifically at least about 1.2 cm and up to about 10 cm. Desirably, an absorbent article of the present invention exhibits an increase in Central Elevation in the target zone of at least about 20%, and more specifically at least about 50%, relative to the Central Elevation in the target zone exhibited by an essentially identical absorbent article without a shaping line.